Production method of phosphor

ABSTRACT

A production method of a phosphor includes firing a starting material mixture in a nitrogen atmosphere at a temperature range between 1,500° C. inclusive and 2,200° C. inclusive. The starting material mixture is a mixture of metallic compounds, and is capable of constituting a composition including M, A, Al, O, and N (M is Eu; and A is one kind or two or more kinds of element(s) selected from C, Si, Ge, Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf, Ta, and W) by firing.

TECHNICAL FIELD

The present invention relates to a production method of a phosphorincluding, as a host crystal, an AlN crystal or AlN solid-solutioncrystal. More particularly, the usage relates to a light emittinginstrument for a lighting instrument and for an image displayingapparatus, utilizing the nature possessed by the phosphor, i.e., theproperty to emit light having a peak at a wavelength between 400 nminclusive and 700 nm inclusive, particularly between 450 nm inclusiveand 520 nm inclusive.

BACKGROUND ART

Phosphors have been utilized for vacuum fluorescent displays (VFD),field emission displays (FED), plasma display panels (PDP), cathode raytubes (CRT), white light emitting diodes (LED), and the like. In allthese usages, it is required to supply an energy to an applicablephosphor to thereby excite it so as to cause it to emit light, and thephosphor is excited by an excitation source having a higher energy suchas vacuum ultraviolet light, ultraviolet light, electron beam, bluelight, or the like, such that the phosphor is caused to emit visiblelight.

However, since phosphors are exposed to the aforementioned excitationsources to resultingly cause a problem of deteriorated luminance,thereby necessitating a phosphor which is free of luminancedeterioration. As such, there have been proposed a sialon phosphor, anoxynitride phosphor, and a nitride phosphor as phosphors each exhibitingless luminance deterioration, instead of the conventional silicatephosphor, phosphate phosphor, aluminate phosphor, sulfide phosphor, andthe like.

One example of the sialon phosphor is produced by a production processas generally described below. Firstly, there are mutually mixed siliconnitride (Si₃N₄), aluminum nitride (AlN), and europium oxide (Eu₂O₃) at apredetermined molar ratio, followed by holding for 1 hour at atemperature of 1,700° C. in nitrogen at 1 atm (0.1 MPa), and firing byhot pressing for production (see patent-related reference 1, forexample). It has been reported that α-sialon obtained by the process andactivated by Eu ion is established into a phosphor which is excited byblue light at 450 to 500 nm and caused to emit yellow light at 550 to600 nm. There has been further known a phosphor provided by adding arare earth element to β-sialon (see patent-related reference 2), and itis shown therein that phosphors activated with Tb, Yb, and Ag areestablished into ones each emitting green light from 525 nm to 545 nm.Moreover, there has been known a green-aimed phosphor provided byactivating β-sialon with Eu²⁺ (see patent-related reference 3).

Examples of oxinitride phosphors include ones each having a JEM phase orLa₃Si₈N₁₁O₄ phase as a host material. Namely, there have been known ablue-aimed phosphor including, as a host crystal, a JEM phase(LaAl(Si_(6-z)Al_(z))N_(10-z)O_(z)) activated with Ce (seepatent-related reference 4), and a blue-aimed phosphor including, as ahost crystal, La₃Si₈N₁₁O₄ activated with Ce (see patent-relatedreference 5).

Known as one example of nitride phosphors is a red-aimed phosphorincluding, as a host crystal, CaAlSiN₃ activated with Eu (seepatent-related reference 6). Further, it is reported in apatent-unrelated reference 1 that there has been obtained anorange-aimed phosphor or red-aimed phosphor having an emission peakbetween 580 nm and 640 nm as a phosphor including AlN as a host crystal,by synthesizing an amorphous ceramic thin-film of AlN:Eu³⁺ by amagnetron sputtering method at a room temperature. It is furtherreported in a patent-unrelated reference 2 that a phosphor obtained byactivating an amorphous AlN thin-film with Tb³⁺ emits green light havinga peak at 543 nm by electron beam excitation. Moreover, there has beenreported a phosphor including an AlN thin-film activated with Gd³⁺ in apatent-unrelated reference 3. However, all the phosphors based on AlNare amorphous thin-films, and are thus unsuitable for usage in a whiteLED, display, and the like.

REFERENCED LITERATURE/PUBLICATION

-   Patent-related reference 1: JP-A-2002-363554-   Patent-related reference 2: JP-A-60-206889-   Patent-related reference 3: Publication matured from Japanese Patent    Application No. 2004-070894-   Patent-related reference 4: Publication matured from Japanese Patent    Application No. 2003-208409-   Patent-related reference 5: Publication matured from Japanese Patent    Application No. 2003-346013-   Patent-related reference 6: Publication matured from Japanese Patent    Application No. 2004-41503-   Patent-unrelated reference 1: Meghan L. Caldwell, et al, MRS    Internet Journal Nitride Semiconductor Research, vol. 6, No. 13, p.    1-8 (2001)-   Patent-unrelated reference 2: H. H. Richardson, et al, Applied    Physics Letters, vol. 80, No. 12, p. 2207-2209 (2002)-   Patent-unrelated reference 3: U. Vetter, et al, Physics Letters,    vol. 83, No. 11, p. 2145-2147 (2003)

However, there have been demanded phosphors aimed at various colors andhaving higher luminances with excellent durability, for usage in whiteLED, plasma display, and the like each having an ultraviolet LED as anexcitation source. Although the phosphors including a JEM phase andLa₃Si₈N₁₁O₄ as host materials, respectively, have been reported asnitride phosphors or oxynitride phosphors emitting blue light, luminancethereof is not regarded as being sufficient, thereby demanding aphosphor for exhibiting a higher luminance.

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The present invention intends to satisfy such a demand, and has anobject to provide a phosphor powder which is more excellent in emissioncharacteristic than the conventional rare-earth activated sialonphosphors and which is more excellent in durability than theconventional oxide phosphors. Particularly, the present invention aimsat providing blue-aimed and red-aimed phosphor powders.

Means for Solving the Problem

Under these circumstances, the present inventors have earnestly andrepeatingly investigated oxynitrides each including an AlN crystal orAlN solid-solution crystal including at least, dissolved therein in asolid state, a metallic element M (M is one kind or two or more kinds ofelement(s) selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb)and oxygen, and have found that those oxynitrides having particularcomposition ranges, particular solid solution states, and particularcrystal phases have higher luminances, and those oxynitrides havingparticular composition ranges are established into blue-aimed phosphorshaving emission peaks at wavelengths within a range between 450 nminclusive and 520 nm inclusive, respectively. The present inventors alsohave found that those oxynitrides having other particular compositionranges are established into red-aimed phosphors having emission peaks atwavelengths within a range between 580 nm inclusive and 650 nminclusive.

Although the patent-unrelated references 1 to 3 have reported that thethin-films obtained by activating AlN amorphous thin-films with Eu³⁺,Tb³⁺, and Gd³⁺, respectively, exhibit emission by electron beamexcitation, it has been never considered to use inorganic compounds eachincluding, as host materials, AlN crystal or AlN solid-solution crystalincluding oxygen, as phosphors, respectively. Namely, the presentinventors have found for the first time such an important discovery thatAlN crystals or AlN solid-solution crystals including, dissolved thereinin a solid state, a particular metallic element and oxygen, can be usedas phosphors exhibiting emission at higher luminances by excitation ofultraviolet light, visible light, electron beam, or X-rays. The presentinventors have earnestly and repetitively conducted investigation basedon the above knowledge, and have succeeded in providing: phosphors whichexhibit emission phenomena at higher luminances over specific wavelengthranges, respectively; a production method of the phosphor; and alighting instrument and an image displaying apparatus based thereon,having excellent characteristics; by achieving configurations recited inthe following items (1) through (47). The above configurations arerecited in the following items (1) through (47).

(1) A phosphor, characterized in that the phosphor comprise an AlNcrystal or AlN solid-solution crystal including, at least: a metallicelement M (M is one kind or two or more kinds of element(s) selectedfrom Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) and oxygen, bothdissolved in the crystal in a solid state; and

that the phosphor emits fluorescence having a peak at a wavelengthwithin a range of 400 nm to 700 nm, by irradiation of an excitationsource.

(2) The phosphor of item (1), characterized in that the AlN crystal orAlN solid-solution crystal has a wurtzite-type AlN crystal structure.

(3) The phosphor of item (1) or (2), characterized in that the AlNsolid-solution crystal has a crystal structure selected from 2Hδ, 27R,21R, 12H, 15R, and 8H.

(4) The phosphor of any one of items (1) through (3), characterized inthat the phosphor includes, at least: the metallic element M of item 1;Al; O; N; and an element A (A is one kind or two or more kinds ofelement(s) selected from C, Si, Ge, Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc,Y, La, Gd, Lu, Ti, Zr, Hf, Ta, and W).

(5) The phosphor of any one of items (1) through (4), characterized inthat the phosphor includes: the metallic element M of item (1); theelement A of item (4); and elements of Al, O, and N; and

that the phosphor is represented by a composition formulaM_(a)Al_(b)A_(c)N_(d)O_(e) (where a+b+c+d+e=1) satisfying the followingconditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v).

(6) The phosphor of item (4) or (5), characterized in that the phosphorincludes at least Si, as the element A.

(7) The phosphor of any one of items (1) through (6), characterized inthat the phosphor includes at least Eu, as the metallic element M.

(8) The phosphor of any one of items (1) through (7), characterized inthat the phosphor is represented by a composition formulaEu_(a)Al_(b)Si_(c)N_(d)O_(e) (where a+b+c+d+e=1) satisfying thefollowing conditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v);

that Eu is divalent; and

that the phosphor has an emission peak wavelength within a range between450 nm inclusive and 520 nm inclusive.

(9) The phosphor of any one of items (1) through (6), characterized inthat the phosphor includes at least Mn, as the metallic element M.

(10) The phosphor of any one of items (1) through (6), characterized inthat the phosphor is represented by a composition formulaMn_(a)Al_(b)Si_(c)N_(d)O_(e) (where a+b+c+d+e=1) satisfying thefollowing conditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v); and

that the phosphor has an emission peak wavelength within a range between560 nm inclusive and 650 nm inclusive.

(11) The phosphor of item (9) or (10), characterized in that thephosphor has an afterglow time of 5 seconds or longer, over which anemission intensity of 1/10 or stronger is kept even after termination ofirradiation of the excitation source.

(12) The phosphor of any one of items (1) through (11), characterized inthat the AlN crystal or AlN solid-solution crystal comprises singlecrystal particles or aggregations of single crystals having an averagedparticle size between 0.1 μm inclusive and 20 μm inclusive.

(13) The phosphor of any one of items (1) through (12), characterized inthat the excitation source is ultraviolet light or visible light havinga wavelength between 100 nm inclusive and 500 nm inclusive.

(14) The phosphor of any one of items (1) through (12), characterized inthat the excitation source is electron beam or X-rays.

(15) A phosphor characterized in that the phosphor comprises a mixtureof: the inorganic compound constituting the phosphor of any one of items(1) through (14); and an additional crystal phase or amorphous phase;and

that the inorganic compound constituting the phosphor of any one ofitems (1) through (14) is included at a content of 10 mass % or more.

(16) The phosphor of item (15), characterized in that the inorganiccompound constituting the phosphor of any one of items (1) through (14)is included at a content of 50 mass % or more.

(17) The phosphor of item (15) or (16), characterized in that theadditional crystal phase or amorphous phase is an inorganic substancehaving electroconductivity.

(18) The phosphor of item (17), characterized in that the inorganicsubstance having electroconductivity is oxide, oxynitride, nitride, or amixture thereof including one kind or two or more kinds of element(s)selected from Zn, Ga, In, and Sn.

(19) A production method of the phosphor of any one of items (1) through(18), characterized in that the method comprises the step of:

firing a starting material mixture in a nitrogen atmosphere at atemperature range between 1,500° C. inclusive and 2,200° C. inclusive,

wherein the starting material mixture is a mixture of metalliccompounds, and is capable of constituting a composition comprising M, A,Si, Al, O, and N (M is one kind or two or more kinds of element(s)selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb; and A isone kind or two or more kinds of element(s) selected from C, Si, Ge, Sn,B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf, Ta, and W) byfiring.

(20) The production method of the phosphor of item (19), characterizedin that the metallic compound mixture is a mixture of: a metal, oxide,carbonate, nitride, fluoride, chloride, or oxynitride of M; siliconnitride; and aluminum nitride.

(21) The production method of the phosphor of item (19) or (20),characterized in that M is Eu.

(22) The production method of the phosphor of item (19) or (20),characterized in that M is Mn.

(23) The production method of the phosphor of any one of items (19)through (22), characterized in that A is Si.

(24) The production method of the phosphor of any one of items (19)through (23), characterized in that the nitrogen atmosphere is a gasatmosphere at a pressure in a range between 0.1 MPa inclusive and 100MPa inclusive.

(25) The production method of the phosphor of any one of items (19)through (24), characterized in that the method further comprises thestep of:

firing the metallic compounds each in a form of powder or aggregations,after filling the metallic compounds in a container in a state where themetallic compounds are held at a filling ratio exhibiting a relativebulk density of 40% or less.

(26) The production method of the phosphor of item (25), characterizedin that the container is made of boron nitride.

(27) The production method of the phosphor of item (25) or (26),characterized in that aggregations have an averaged aggregation size of500 μm or less.

(28) The production method of the phosphor of any one of items (19)through (27), characterized in that the firing step is conducted not bymeans of hot-press, but exclusively by means of gas pressure sintering.

(29) The production method of the phosphor of any one of items (19)through (28), characterized in that the method further comprises thestep of:

adjusting the synthesized phosphor powder in granularity, to cause thesame to have an averaged particle size between 50 nm inclusive and 20 μminclusive, by a single or multiple procedures selected frompulverization, classification, and acid treatment.

(30) The production method of the phosphor of any one of items (19)through (29), characterized in that the method further comprises thestep of:

heat treating the phosphor powder after firing, the phosphor powderafter pulverization treatment, or the phosphor powder after granularityadjustment, at a temperature between 1,000° C. inclusive and the firingtemperature inclusive.

(31) The production method of the phosphor of any one of items (19)through (30), characterized in that the method further comprises thestep of:

before the firing step, adding an inorganic compound for generating aliquid phase at the firing temperature or below, into the mixture ofmetallic compounds.

(32) The production method of the phosphor of item (31), characterizedin that the inorganic compound for generating the liquid phase at thefiring temperature or below, is one kind or a combination of two or morekinds of fluoride, chloride, iodide, bromide, and phosphate of one kindor two or more kinds of element(s) selected from Li, Na, K, Mg, Ca, Sr,Ba, and Al.

(33) The production method of the phosphor of item (31) or (32),characterized in that the inorganic compound for generating the liquidphase at the firing temperature or below, is calcium fluoride oraluminum fluoride.

(34) The production method of the phosphor of any one of items (31)through (33), characterized in that the inorganic compound forgenerating the liquid phase at the firing temperature or below, is addedat an amount between 0.1 parts by weight inclusive and 10 parts byweight inclusive, relative to 100 parts by weight of the mixture ofmetallic compounds.

(35) The production method of the phosphor of any one of items (19)through (34), characterized in that the method further comprises thestep of:

washing the product after firing by a solvent comprising water or anacidic water solution, to thereby decrease contents of a glass phase,second phase, or impurity phase included in the product.

(36) The production method of the phosphor of item (35), characterizedin that the acid comprises a single or a combination of sulfuric acid,hydrochloric acid, nitric acid, hydrofluoric acid, and organic acids.

(37) The production method of the phosphor of item (35) or (36),characterized in that the acid is a mixture of hydrofluoric acid andsulfuric acid.

(38) A lighting instrument constituted of a light-emitting source and aphosphor, characterized in that the phosphor of at least one of items(1) through (18) is used.

(39) The lighting instrument of item (38), characterized in that thelight-emitting source is a light emitting diode (LED) or laser diode(LD) for emitting light at a wavelength of 330 to 500 nm.

(40) The lighting instrument of item (38) or (39), characterized in thatthe light-emitting source is an LED or LD for emitting light at awavelength between 330 and 420 nm; and

that the constituent phosphor is provided by adopting: the phosphor ofany one of items (1) through (18); a green-aimed phosphor having anemission peak at a wavelength between 520 nm and 550 nm by pump lightbetween 330 and 420 nm; and a red-aimed phosphor having an emission peakat a wavelength between 600 nm and 700 nm by pump light between 330 and420 nm; so that the constituent phosphor emits white light mixedlyincluding blue light, green light, and red light.

(41) The lighting instrument of item (38) or (39), characterized in thatthe light-emitting source is an LED or LD for emitting light at awavelength between 330 and 420 nm; and

that the constituent phosphor is provided by adopting: the phosphor ofany one of items (1) through (18); a green-aimed phosphor having anemission peak at a wavelength between 520 nm and 550 nm by pump lightbetween 330 and 420 nm; a yellow-aimed phosphor having an emission peakat a wavelength between 550 nm and 600 nm by pump light between 330 and420 nm; and a red-aimed phosphor having an emission peak at a wavelengthbetween 600 nm and 700 nm by pump light between 330 and 420 nm; so thatthe constituent phosphor emits white light mixedly including blue light,green light, yellow light, and red light.

(42) The lighting instrument of item (40) or (41), characterized in thatthe green-aimed phosphor is β-sialon activated with Eu.

(43) The lighting instrument of item (40) or (41), the red-aimedphosphor is CaAlSiN₃ activated with Eu.

(44) The lighting instrument of item (41), characterized in that theyellow-aimed phosphor is Ca-α-sialon activated with Eu.

(45) An image displaying apparatus constituted of an excitation sourceand a phosphor, characterized in that the phosphor of at least one ofitems (1) through (18) is used.

(46) The image displaying apparatus of item (45), characterized in thatthe excitation source is electron beam, electric field, vacuumultraviolet light, or ultraviolet light.

(47) The image displaying apparatus of item (45) or (46), characterizedin that the image displaying apparatus is a vacuum fluorescent display(VFD), field emission display (FED), plasma display panel (PDP), orcathode ray tube (CRT).

Effect of the Invention

The phosphors of the present invention each contain, as a maincomponent, an AlN crystal or AlN solid-solution crystal phase to therebyexhibit a higher emission intensity within a wavelength range of 400 nmto 700 nm as compared with the conventional sialon phosphors andoxynitride phosphors, and among them, the phosphors of the presentinvention activated with Eu are excellent as blue-aimed or green-aimedphosphors, and the phosphors of the present invention activated with Mnare excellent as red-aimed phosphors. Further, the phosphors of thepresent invention serve as useful ones exhibiting such remarkablefunctions and effects that the phosphors are stably functionable as andusable as VFD, FED, PDP, CRT, white LED, and the like without luminancedeterioration even when exposed to excitation sources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an X-ray diffraction chart of an inorganic compound of Example1.

FIG. 2 is a graph of particle size distribution of the inorganiccompound of Example 1.

FIG. 3 is an electron micrograph as an observation result of theinorganic compound of Example 1 by a scanning electron microscope (SEM).

FIG. 4 is a graph of an excitation spectrum and an emission spectrum ofExample 1 based on fluorometry.

FIG. 5 is a schematic view of a lighting instrument (LED lightinginstrument) according to the present invention.

FIG. 6 is a schematic view of an image displaying apparatus (plasmadisplay panel) according to the present invention.

FIG. 7 is a graph of an excitation spectrum and an emission spectrum ofan inorganic compound of Example 27 based on fluorometry.

FIG. 8 is a graph of long afterglow property of an inorganic compound ofExample 27.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 mixture of green-aimed phosphor (Example 1) of the present        invention, red-aimed phosphor, and blue-aimed phosphor; mixture        of green-aimed phosphor (Example 1) of the present invention and        red-aimed phosphor; or mixture of green-aimed phosphor        (Example 1) of the present invention and yellow-aimed phosphor    -   2 LED chip    -   3, 4 electroconductive terminal    -   5 wire bond    -   6 resin layer    -   7 vessel    -   8 red-aimed phosphor    -   9 green-aimed phosphor    -   10 blue-aimed phosphor    -   11, 12, 13 ultraviolet emission cell    -   14, 15, 16, 17 Electrode    -   18, 19 dielectric layer    -   20 protection layer    -   21, 22 glass substrate

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail, based on Examples.

The phosphors of the present invention each include an AlN crystal orAlN solid-solution crystal as a main component. The AlN crystal is onehaving a wurtzite-type crystal structure. Further, the AlNsolid-solution crystal includes AlN having silicon, oxygen, and the likeadded thereto, and is one such as:

2Hδ: Si_(2.40)Al_(8.60)O_(0.60)N_(11.40)

27R: Al₉O₃N₇:1Al₂O₃-7AlN

21R: Al₇O₃N₅:1Al₂O₃-5AlN

12H: SiAl₅O₂N₅:1SiO₂-5AlN

15R: SiAl₄O₂N₄:1SiO₂-4AlN, or

8H: Si_(0.5)Al_(3.5)O_(2.5)N_(2.5):0.5SiO₂-0.5Al₂O₃-2.5AlN.

In the present invention, these crystals can each be used as a hostcrystal. The AlN crystal or AlN solid-solution crystal can be identifiedby X-ray diffraction, neutron beam diffraction, and the like; and, inaddition to those substances exhibiting the same diffraction as the pureAlN crystal and AlN solid-solution crystal, those AlN crystals and AlNsolid-solution crystals are also embraced within the present inventionwhich have lattice constants changed by substitution of constituentelements by other elements.

According to the present invention, dissolving, in a solid state, ametallic element M and oxygen in an AlN crystal or AlN solid-solutioncrystal as a host crystal, provides a phosphor having excellent opticalcharacteristics. Here, the metallic element M is one to be matured intoa photoactive ion, and is one kind or two or more kinds of element(s)selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb, in amanner that these elements are excited by ultraviolet light, electronbeam, or the like to exhibit emission to thereby establish a phosphoremitting fluorescence having a peak at a wavelength within a range of400 nm to 700 nm. Among them, phosphors including Eu serve asparticularly excellent ones emitting blue to green light at higherluminance. Further, phosphors including Mn serve as red-aimed ones withhigher luminance. The effect of oxygen is considered to cause the M tobe readily dissolved in the host crystal in a solid state by virtue ofcombination of the M with oxygen, thereby resultingly contributing toimproving luminance of the applicable phosphor.

Embraced as one of embodiments of the present invention is a phosphorincluding, at least, a metallic element M, Al, O, N, and an element A (Ais one kind or two or more kinds of element(s) selected from C, Si, Ge,Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf, Ta, andW). Inclusion of the element A compensates for electric charge tothereby stabilize the crystal structure including M and O dissolvedtherein in a solid state, thereby improving the phosphor in luminance.Among them, those inorganic compounds each including Si as the element Aare established into phosphors having higher luminance, respectively.

The following ranges are desirable for compositions for allowingobtainment of phosphors including AlN crystals or AlN solid-solutioncrystals at higher ratios and exhibiting higher luminances,respectively. Namely, the phosphors are each represented by acomposition formula M_(a)Al_(b)A_(c)N_(d)O_(e) (where a+b+c+d+e=1), andeach include elements of M (M is one kind or two or more kinds ofelement(s) selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, andYb), A (A is one kind or two or more kinds of element(s) selected fromC, Si, Ge, Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf,Ta, and W), and elements of Al, O, and N, in which the parameters a, b,c, d, and e are selected from values satisfying all the followingconditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v).

The “a” value represents an adding amount of the element M to be maturedinto an emission center, and is preferably set between 0.00001 inclusiveand 0.1 inclusive in atomic ratio.

“a” values less than 0.00001 lead to smaller numbers of M acting asemission centers, thereby deteriorating emission luminances. “a” valueslarger than 0.1 cause concentration quenching due to interference amongM ions, thereby deteriorating luminances. The “b” value represents anamount of an Al element constituting the host crystal, and is preferablyset between 0.4 inclusive and 0.55 inclusive in atomic ratio.

Deviation of the “b” value from this range leads to unstable bonds inthe crystal to increase a generation ratio of crystal phases other thanthe AlN crystal or AlN solid-solution crystal, thereby deterioratingemission intensity.

The “c” value represents an amount of the A element, and is preferablyset between 0.001 inclusive and 0.1 inclusive in atomic ratio. “c”values less than 0.001 lead to poor effects of electric chargecompensation to obstruct solid-state dissolution of M and O, therebydeteriorating luminance. “c” values larger than 0.1 increase ageneration ratio of crystal phases other than the AlN crystal or AlNsolid-solution crystal, thereby deteriorating emission intensity.

The “d” value represents an amount of nitrogen, and is preferably setbetween 0.4 inclusive and 0.55 inclusive in atomic ratio. Deviation ofthe “d” value from this range increases a generation ratio of crystalphases other than the AlN crystal or AlN solid-solution crystal, therebydeteriorating emission intensity.

The “e” value represents an amount of oxygen, and is preferably setbetween 0.001 inclusive and 0.1 inclusive in atomic ratio. “e” valuesless than 0.001 obstruct solid-state dissolution of M, therebydeteriorating luminance. “e” values larger than 0.1 increase ageneration ratio of crystal phases other than the AlN crystal or AlNsolid-solution crystal, thereby deteriorating emission intensity.

Embraced as ones of embodiments of the present invention are phosphorswhere M is Eu and A is Si. Among them, those phosphors serve asblue-aimed ones having peak wavelengths within a range between 450 nminclusive and 520 nm inclusive, which are each represented by acomposition formula Eu_(a)Al_(b)Si_(c)N_(d)O_(e) (where a+b+c+d+e=1) andthe parameters a, b, c, d, and e satisfy the following conditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v).

In the above, Eu acts as divalent Eu to contribute to emission.

As ones of embodiments of the present invention, those phosphors where Mis Mn are established into red-aimed ones. Among them, those phosphorsserve as red-aimed ones having peak wavelengths within a range between560 nm inclusive and 650 nm inclusive, which are each represented by acomposition formula Mn_(a)Al_(b)Si_(c)N_(d)O_(e) (where a+b+c+d+e=1) andthe parameters a, b, c, d, and e satisfy the following conditions:

0.00001≦a≦0.1  (i),

0.4≦b≦0.55  (ii),

0.001≦c≦0.1  (iii),

0.4≦d≦0.55  (iv), and

0.001≦e≦0.1  (v).

Those phosphors where M is Mn, each have a long afterglow property.“Long afterglow” means a phenomenon that emission continues even afterterminating irradiation of excitation source, and leads to a phosphorsuitable as a sign lighting and a mark at night and during power outage.The phosphors of the present invention including Mn each exhibit such aproperty to have an afterglow time of 5 seconds or longer, where theafterglow time means a period of time over which an emission intensityof 1/10 or stronger is kept even after termination of irradiation ofpump light.

In case of utilizing the phosphor of the present invention as a powder,averaged particle sizes between 0.1 μm inclusive and 20 μm inclusive aredesirable, from standpoints of dispersibility into resin, flowability ofthe powder, and the like. Additionally, making the powder as singlecrystal particles in this range, further improves emission luminance.

The phosphors of the present invention are desirably excited byultraviolet light or visible light having wavelengths between 100 nminclusive and 500 nm inclusive, to thereby effectively emit light. Thephosphors of the present invention can also be excited by electron beamor X-rays.

The phosphors of the present invention emit fluorescence having peaks atwavelengths within a range of 400 nm to 700 nm, by irradiation of anexcitation source thereto. Particularly, emission colors in spectra ofsharp shapes having peaks at wavelengths within a range of 420 nm to 550nm take values of 0≦x≦0.3 and 0.1≦y≦0.95 in terms of (x, y) values onCIE chromaticity coordinates, thereby exhibiting blue light or greenlight with excellent color purity.

In the present invention, although the AlN crystal or AlN solid-solutioncrystal acting as constituent components are to be highly pure and to beincluded as much as possible, and are to be possibly and desirablyconstituted of a single phase from a standpoint of fluorescenceemission, it is also possible to constitute the crystal by a mixturewith an additional crystal phase or amorphous phase within an extentwhere due properties are not deteriorated. In this case, it is desirablethat the content of AlN crystal or AlN solid-solution crystal is 10 mass% or more, preferably 50 mass % or more, so as to obtain higherluminance. For the range of the main component in the present invention,the content of the AlN crystal or AlN solid-solution crystal is at least10 mass % or more. The content ratio of the AlN crystal or AlNsolid-solution crystal can be obtained from a ratio between strongestpeaks of phases of the above crystal and the other crystals, byconducting X-ray diffraction measurement.

In case of phosphors each constituted of mixtures with another crystalphase or amorphous phase, the phosphors may be mixtures with inorganicsubstances having electroconductivity. In case that the phosphors of thepresent invention are each excited by electron beam in VFD, PDP, and thelike, the phosphors each preferably have a certain electroconductivityso as to release electrons to the exterior without remaining on thephosphors. Examples of electroconductive substances include oxides,oxynitrides, nitrides, and mixtures thereof including one kind or two ormore kinds of element(s) selected from Zn, Ga, In, and Sn. Among them,indium oxide and indium-tin oxide (ITO) are desirable by virtue of lessdeterioration of fluorescence intensity and higher electroconductivity.

Although the phosphors including Eu of the present invention emit bluelight or green light, it is possible to mix inorganic phosphorstherewith which emit other color(s) such as yellow, red, and the like asrequired, when the blue color or green color is required to be mixedwith such other color(s).

The phosphors of the present invention have different excitation spectraand fluorescence spectra depending on compositions, respectively, andappropriate selections and combinations thereof allow for obtainment ofvarious emission spectra. The configurations may be set at spectrarequired based on usages, respectively.

Although the phosphors of the present invention are not particularlydefined in production method, examples thereof include the followingmethods.

It is possible to obtain the phosphor of the present invention byfiring, in a nitrogen atmosphere at a temperature range between 1,500°C. inclusive and 2,200° C. inclusive, a starting material mixture ormetallic compound mixture which is capable of constituting a compositionincluding M, A, Si, Al, O, and N (M is one kind or two or more kinds ofelement(s) selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb;and A is one kind or two or more kinds of element(s) selected from C,Si, Ge, Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf,Ta, and W) by firing. Although optimum firing temperatures can not besweptly defined because they differ depending on compositions, it ispossible to obtain higher luminance phosphors within a temperature rangebetween 1,820° C. inclusive and 2,000° C. inclusive, in case ofM_(a)Al_(b)Si_(c)N_(d)O_(e) system (M=Eu, Ce, or Yb). Firingtemperatures below 1,500° C. cause the element M acting as an emissioncenter to remain at a grain boundary phase having a higher oxygencontent without dissolving, in a solid state, in the AlN crystal or AlNsolid-solution crystal, to thereby exhibit emission based on oxide glassas a host, thereby failing to obtain a higher luminance fluorescence.Further, firing temperatures above 2,200° C. are industriallydisadvantageous, due to necessity of a specific apparatus.

The patent-unrelated references 1 to 3 are related to synthesis at roomtemperature where the element M dissolves in an amorphous substance in asolid state. Namely, although the patent-unrelated reference 1 adopts Euas an activation element identically to the present invention, itsemission wavelength corresponds to red color of 600 nm or longer, whichis essentially different from emission wavelengths between 450 nminclusive and 520 nm inclusive by the phosphors of the presentinvention.

The mixtures of metallic compounds of the present invention arepreferably those including M, which are selected from metals, oxides,carbonates, nitrides, and oxynitrides of Al, M, and A. In case that A isSi, mixtures of silicon nitride, aluminum nitride, and oxides of M arepreferable. These are rich in reactivity and obtainable as high puritysynthetics, and advantageously and readily available since they areproduced as industrial materials.

To improve reactivity upon firing, it is possible to add an inorganiccompound for generating a liquid phase at the firing temperature orbelow, into the mixture of metallic compounds as required. Examples ofsuitable inorganic compounds include those which generate stable liquidphases at reaction temperatures, respectively, such as fluorides,chlorides, iodides, bromides, or phosphates of Li, Na, K, Mg, Ca, Sr,Ba, and Al elements. Without limited to addition of a simple substance,these inorganic compounds may be mixed based on two or more kinds. Amongthem, calcium fluoride and aluminum fluoride are suitable, because theyhave higher abilities to improve reactivities for synthesis. Althoughadding amounts of inorganic compounds are not particularly limited,there is obtained a particularly remarkable effect by amounts between0.1 parts by weight inclusive and 10 parts by weight inclusive relativeto 100 parts by weight of mixture of metallic compounds as a startingmaterial. Amounts less than 0.1 parts by weight lead to less improvementof reactivity, and amounts exceeding 10 parts by weight deteriorateluminances of phosphors. Firing with addition of these inorganiccompounds improves reactivities, thereby promoting grain growth in arelatively short time to grow a single crystal having larger particlesizes, to improve luminance of the phosphor.

The nitrogen atmosphere is preferably a gas atmosphere within a pressurerange between 0.1 MPa inclusive and 100 MPa inclusive. Pressures between0.5 MPa inclusive and 10 MPa inclusive are more preferable. In case ofadopting silicon nitride as a starting material and heating it to atemperature of 1,820° C. or higher, nitrogen gas atmospheres of 0.1 MPaor lower are disadvantageous due to thermal decomposition of thestarting material. Decomposition is rarely caused at 0.5 MPa or higher.10 MPa is sufficient, and excess of 100 MPa requires a special apparatusand is unsuitable for industrial production.

In case of adopting a fine powder having a particle size of several μmas a starting material, the mixture of metallic compounds afterfinishing a mixing process exhibits a configuration where the finepowder having the particle size of several μm has aggregated intoparticles (hereinafter called “powder aggregation”) having sizes ofseveral hundreds μm to several mm. In the present invention, the powderaggregations are fired in a state that they are held at a filling ratioexhibiting a bulk density of 40% or less. Here, the relative bulkdensity indicates a ratio between: a value (bulk density) obtained bydividing a mass of a powder filled in a container, by a volume of thecontainer; and a true density of the powder substance. Namely, althoughfiring is conducted for a powder in a state of higher filling ratioafter hot pressing or mold shaping in case of typical production ofsialon, the present invention is so configured that powder aggregationsof a mixture equalized in granularity are directly filled into acontainer at a filling ratio exhibiting a bulk density of 40% or less,without applying a mechanical force to the powder and without previouslyadopting a mold or the like. The powder aggregations can be controlledin granularity as required, by granulating the powder aggregations tohave an averaged aggregation size of 500 μm or less by a sieve, airclassification, or the like. It is also possible to directly granulatethem into shapes of 500 μm or less, by a spray drier or the like.Further, adoption of a container made of boron nitride exhibits anadvantage of less reactivity with a phosphor.

The reason, why the starting material powder is to be fired in the statewhere its bulk density is held at 40% or less, is as follows. Namely,firing the powder in a state where free spaces are left around thepowder, causes the crystals of reaction products to grow into the freespaces with less contact among the crystals, thereby enabling synthesisof a crystal having fewer surface defects. This allows for obtainment ofa phosphor of higher luminance. Bulk densities exceeding 40% causepartial densification during firing to result in a densely sintered bodywhich obstructs crystal growth, thereby deteriorating luminance of aphosphor. Further, fine powders can not be obtained. Moreover, powderaggregation sizes of 500 μm or less are particularly desirable, byvirtue of excellent pulverizability after firing.

Next, powder aggregations having a filling ratio of 40% or less arefired under the above conditions. Since the firing temperature is highand the firing environment is nitrogen, the furnace to be used forfiring is preferably an electric one in a metal resistance heating typeor black lead resistance heating type which utilizes carbon as amaterial for the hot portion of the furnace. The firing procedure ispreferably a sintering procedure such as an ordinary pressure sinteringmethod or a gas pressure sintering method where no mechanicalpressurization is applied from the exterior, so as to conduct firingwhile keeping the bulk density high.

When the powder aggregations obtained by firing are firmly solidified,the same are to be pulverized by a pulverizer such as a ball mill, jetmill, or the like to be commonly used in factories. Among them, ballmill pulverization is easy in particle size control. Balls and pot to beused then are preferably made of silicon nitride sintered bodies orsialon sintered bodies. Particularly desirable are sintered bodies of aceramic having the same composition as the phosphor to be establishedinto a product. The pulverization is to be conducted until the averagedparticle size becomes 20 μm or less. Particularly desirably, theaveraged particle size is between 20 nm inclusive and 5 μm inclusive.Averaged particle sizes exceeding 20 μm lead to a deterioratedflowability of the powder and deteriorated dispersibility thereof in theresin, and lead to non-uniform emission intensities site by site uponfabricating a light emitting apparatus by combination with a lightemitting element. Averaged particle sizes of 20 nm or less lead todeteriorated operability of the powder. Classification may be combinedlyused, when intended particle sizes are not obtained by pulverizationonly. Usable as techniques of classification are sieving, airclassification, precipitation in liquid, and the like.

Washing the reaction product obtained by firing after firing by asolvent for dissolving inorganic compounds therein, allows for decreaseof contents of inorganic compounds other than the phosphor such as aglass phase, second phase, and impurity phase included in the reactionproduct, thereby improving luminance of the phosphor. Usable as such asolvent are water, and an acidic water solution. Usable as the acidicwater solution are sulfuric acid, hydrochloric acid, nitric acid,hydrofluoric acid, and a mixture of organic acid and hydrofluoric acid.Among them, the mixture of sulfuric acid and hydrofluoric acid has alarger effect. This treatment has a particularly remarkable effect for areaction product obtained by firing at a high temperature by addition ofan inorganic compound which generates a liquid phase at the firingtemperature or below.

Although the above process allows for obtainment of a fine powder ofphosphor, heat treatment is effective for further improvement ofluminance. In this case, the powder after firing or the powder aftergranularity adjustment by pulverization, classification, or the like canbe heat treated at a temperature between 1,000° C. inclusive and thefiring temperature inclusive. Temperatures below 1,000° C. lead to aless effect of eliminating surface defects. Temperatures above thefiring temperature are disadvantageous, due to re-fixation among oncepulverized powder particles. Although atmospheres suitable for heattreatment differ depending on compositions of phosphors, it is possibleto use a mixed atmosphere of one kind or two or more kinds selected fromnitrogen, air, ammonia, and hydrogen, and a nitrogen atmosphere isdesirable by virtue of an excellent effect of defect elimination.

The phosphors of the present invention obtained in the above manner arecharacterized in that they exhibit emission of visible light at higherluminance, as compared with typical oxide phosphors, existing sialonphosphors, and the like. Among them, particular compositions arecharacterized in that they exhibit emission of blue light or green lighthaving peaks within a range between 420 nm inclusive and 550 nminclusive, and are suitable for a lighting instrument and an imagedisplaying apparatus. In addition thereto, the phosphors of the presentinvention are excellent in heat resistance because they are not degradedeven by exposure to high temperatures, and are also excellent inlong-term stability in an oxidative atmosphere and under a moistureenvironment.

The lighting instrument of the present invention is constituted of atleast a light-emitting source and the phosphor of the present invention.Examples of the lighting instruments include an LED lighting instrument,a fluorescent lamp, and the like. LED lighting instruments can beproduced by utilizing the phosphors of the present invention, based onthe known methods such as described in JP-A-5-152609, JP-A-7-99345,JP-2927279, and the like. In this case, desirable examples oflight-emitting sources include ones for emitting light at wavelengths of330 to 500 nm, and particularly, ultraviolet (or violet) LED lightemitting elements or LD light emitting elements for 330 to 420 nm, orblue LED light emitting elements or LD light emitting elements for 420to 500 nm.

Such light emitting elements include ones comprising nitridesemiconductor such as GaN, InGaN, or the like, which can be made intolight-emitting sources for emitting light at predetermined wavelengthsby composition adjustment.

In addition to the way to solely adopt the phosphor of the presentinvention in a lighting instrument, it is possible to constitute alighting instrument for emitting light in a desired color by combininglyusing a phosphor having another emission characteristic. Examplesthereof include a combination of: an ultraviolet LED light emittingelement or LD light emitting element of 330 to 420 nm; a green-aimedphosphor to be excited at the above-mentioned wavelength to thereby emitlight at a wavelength between 520 nm inclusive and 550 nm inclusive; ared-aimed phosphor to be similarly excited to thereby emit light at awavelength between 600 nm inclusive and 700 nm inclusive; and theblue-aimed phosphor of the present invention. Examples of suchgreen-aimed phosphors include β-sialon:Ee²⁺ described in Japanese PatentApplication No. 2004-070894, and examples of such red-aimed phosphorsinclude CaSiAlN₃:Eu²⁺ described in Japanese Patent Application No.2003-394855. In this configuration, ultraviolet rays emitted by the LEDor LD are irradiated to the phosphors which then emit light in threecolors of red, green, and blue, which are mixed to establish a lightinginstrument for emitting white light.

Another way includes a combination of: an ultraviolet LED or LD lightemitting element between 330 to 420 nm; a green-aimed phosphor to beexcited at the above-mentioned wavelength to thereby have an emissionpeak at a wavelength between 520 nm inclusive and 550 nm inclusive; ayellow-aimed phosphor to be excited at the above-mentioned wavelength tothereby have an emission peak at a wavelength between 550 nm inclusiveand 600 nm inclusive; a red-aimed phosphor to be excited at theabove-mentioned wavelength to thereby have an emission peak at awavelength between 600 nm inclusive and 700 nm inclusive; and thephosphor of the present invention. Examples of such green-aimedphosphors include β-sialon:Eu²⁺ described in Japanese Patent ApplicationNo. 2004-070894, examples of such yellow-aimed phosphors includeα-sialon:Ee²⁺ described in JPA-2002-363554, or (Y, Gd)₂(Al, Ga)₅O₁₂:Cedescribed in JP-A-9-218149, and examples of such red-aimed phosphorsinclude CaSiAlN₃:Eu²⁺ described in Japanese Patent Application No.2003-394855. In this configuration, ultraviolet light emitted by the LEDor LD is irradiated to the phosphors which then emit light in fourcolors of blue, green, yellow, and red, which are mixed to establish alighting instrument for emitting light in white or reddish incandescentcolor.

The image displaying apparatus of the present invention is constitutedof at least an excitation source and the phosphor of the presentinvention, and examples thereof include a vacuum fluorescent display(VFD), field emission display (FED), plasma display panel (PDP), cathoderay tube (CRT), and the like. It has been confirmed that the phosphorsof the present invention can each emit light by excitation of vacuumultraviolet light from 100 to 190 nm, ultraviolet light from 190 to 380nm, electron beam, and the like, and combining such an excitation sourcewith the phosphor of the present invention enables establishment of suchan image displaying apparatus as described above.

Although the present invention will be detailedly described based on thefollowing Examples, these Examples are disclosed to merely aid inreadily understanding the present invention, without limiting thepresent invention thereto.

Example 1

Used as starting material powders were: a silicon nitride powder havingan averaged particle size of 0.5 μm, an oxygen content of 0.93 wt %, andan α-type content of 92%; an aluminum nitride powder having a specificsurface area of 3.3 m²/g and an oxygen content of 0.79%; and a europiumoxide powder having a purity of 99.9%.

To obtain a compound represented by a composition formulaEu_(0.002845)Al_(0.463253)Si_(0.02845)N_(0.501185)O_(0.004267) (Table 1shows a designed composition, and a mixture composition of startingmaterial powders), there were weighed 6.389 wt %, 91.206 wt %, and 2.405wt % of a silicon nitride powder, an aluminum nitride powder, and aeuropium oxide powder; the powders were then mutually mixed for twohours by a wet-type ball mill adopting a pot made of silicon nitridesintered body, balls made of silicon nitride sintered bodies, andn-hexane. The n-hexane was removed by a rotary evaporator, to obtain adried substance of the mixed powders. The obtained mixture waspulverized by an agate mortar and an agate pestle, followed by passagethrough a sieve of 500 μm, to obtain powder aggregations excellent inflowability. The powder aggregations were naturally dropped and loadedinto a crucible made of boron nitride having dimensions of 20 mmdiameter and 20 mm height, thereby exhibiting a bulk density of 30volume %. The bulk density was calculated from the weight of the loadedpowder aggregations, the inner volume of the crucible, and the truedensity (3.1 g/cm³) of the powder. Next, the crucible was set into anelectric furnace of black lead resistance heating type. There wasconducted a firing operation by firstly bringing the firing environmentto vacuum by a diffusion pump, heating from a room temperature up to800° C. at a rate of 500° C./hour, introducing nitrogen at a purity of99.999 vol % at 800° C. to achieve a pressure of 1 MPa, elevating thetemperature to 2,000° C. at a rate of 500° C./hour, and holding for 2hours at 2,000° C.

The synthesized specimen was pulverized into a powder by an agatemortar, and there was conducted a powder X-ray diffraction measurement(XRD) by Kα line of Cu. The resultingly obtained chart showed a patternof FIG. 1, thereby showing that a crystal of wurtzite-type AlN structurewas generated.

The powder was measured by a spectrophotofluorometer to provide anemission spectrum and an excitation spectrum, thereby resultinglyshowing that the powder was a phosphor having a peak at 334 nm in theexcitation spectrum, and a peak at blue light of 471 nm in the emissionspectrum based on the excitation of 334 nm. The emission intensity atthe peak was 1.402 count. Note that the count value has an arbitraryunit, since it varies depending on a measurement device, a measurementcondition, and the like. Namely, comparison is allowed only amongExamples of the present invention and Comparative Examples measuredunder the same condition. In the present invention, the count value isindicated by standardization such that the emission intensity of acommercially available YAG:Ce phosphor (P46Y3: produced by KASEIOPTONIX, LTD.) becomes 1 upon excitation at 450 nm.

The powder was roughly pulverized, followed by addition of 10 ml ofhydrofluoric acid, 10 ml of sulfuric acid, and 380 ml of distilled waterwithin a beaker of Teflon (Registered Trade-Mark), and application ofstirring operation for two hours at a room temperature. Filtrationdrying was conducted after sufficient washing by distilled water.Measurement of a particle size distribution showed that most ofparticles had particle sizes of 1 μm to 10 μm as shown in FIG. 2, andhad an averaged particle size of 3.2 μm.

The form of the powder was observed by a scanning electron microscope(SEM). As shown in FIG. 3, it was confirmed that the particles were eachisolated and had an idiomorphic form in a flattened plate shape.

The powder was irradiated by a lamp emitting light at a wavelength of365 nm, thereby confirming that the powder emitted blue light. Thepowder was measured by a spectrophotofluorometer to provide an emissionspectrum and an excitation spectrum (FIG. 4), thereby resultinglyshowing that the powder was a phosphor having a peak at 327 nm in theexcitation spectrum, and a peak at blue light of 472 nm in the emissionspectrum based on the excitation of 327 nm. The emission intensity atthe peak was 1.973 count. Namely, the emission intensity was improved by1.4 times by acid treatment. The light emitted by excitation at 365 nmwas blue having a CIE chromaticity of x=0.18 and y=0.19. There wasobserved an emission characteristic (cathode luminescence; CL) uponirradiation of electron beam by a SEM having a CL detector, to evaluatea CL image. This device is configured to detect visible light generatedby irradiation of electron beam to thereby obtain a photograph image astwo-dimensional information, thereby clarifying as to what wavelength oflight is emitted at which site. By the emission spectrum observation, itwas confirmed that the phosphor exhibited emission of blue light at awavelength of 470 nm by excitation of electron beam. Further, accordingto a CL image based on observation of several tens of particles, it wasconfirmed that no locations were found where particular sites emittedlight, and that the insides of the particles uniformly emitted greenlight. It was further confirmed that no particles were found whichemitted light exclusively strongly, and all the several tens ofparticles uniformly emitted green light.

TABLE 1 Designed composition and mixture composition of ExamplesDesigned composition Eu Al Si N O Mixture composition (mass %) Ex. a b cd e Si₃N₄ AlN Eu₂O₃ 1 0.002845 0.463253 0.02845 0.501185 0.004267 6.38991.206 2.405 2 0.002599 0.405803 0.077956 0.509744 0.003898 17.57880.217 2.205 3 0.002716 0.433228 0.054323 0.505659 0.004074 12.22685.474 2.301 4 0.002914 0.479359 0.01457 0.498786 0.004371 3.269 94.2712.46 5 0.000951 0.465525 0.028531 0.503566 0.001427 6.481 92.706 0.813 60.001946 0.480545 0.014591 0.5 0.002918 3.292 95.055 1.652 7 0.0018990.464387 0.02849 0.502374 0.002849 6.435 91.951 1.614 8 0.001855 0.448980.041744 0.504638 0.002783 9.437 88.984 1.579 9 0.002879 0.4712090.021593 0.5 0.004319 4.847 92.721 2.432 10 0.002812 0.455483 0.0351450.502343 0.004217 7.897 89.725 2.378 11 0.002779 0.447893 0.0416860.503474 0.004169 9.372 88.277 2.351 12 0.00388 0.478177 0.0145490.497575 0.00582 3.245 93.498 3.257 13 0.003788 0.462121 0.028409 0.50.005682 6.344 90.472 3.184 14 0.0037 0.446809 0.041628 0.502313 0.005559.308 87.579 3.114 15 0.005666 0.459868 0.028329 0.497639 0.008499 6.25689.035 4.709 16 0.007533 0.457627 0.028249 0.495292 0.011299 6.17187.636 6.193

Examples 2 to 16

To obtain each composition shown in Table 1 by adopting the samestarting material powders as Example 1, there were weighed predeterminedamounts of a silicon nitride powder, an aluminum nitride powder, and aeuropium oxide powder; the powders were then mutually mixed for twohours by a wet-type ball mill adopting a pot made of silicon nitridesintered body, balls made of silicon nitride sintered bodies, andn-hexane. The n-hexane was removed by a rotary evaporator, to obtain adried substance of the mixed powders. The obtained mixture waspulverized by an agate mortar and an agate pestle, followed by passagethrough a sieve of 500 μm, to obtain powder aggregations excellent inflowability. The powder aggregations were naturally dropped and loadedinto a crucible made of boron nitride having dimensions of 20 mmdiameter and 20 mm height. Next, the crucible was set into an electricfurnace of black lead resistance heating type. There was conducted afiring operation by firstly bringing the firing environment to vacuum bya diffusion pump, heating from a room temperature up to 800° C. at arate of 500° C./hour, introducing nitrogen at a purity of 99.999 vol %at 800° C. to achieve a pressure of 1 MPa, elevating the temperature to1,900° C. at a rate of 500° C./hour, and holding for 2 hours at thattemperature. According to X-ray diffraction, all the obtained firedbodies included 50 mass % or more of AlN or AlN solid solution, therebyobtaining phosphors emitting green light having peaks at wavelengthsbetween 471 nm and 480 nm by excitation of ultraviolet light to visiblelight as shown in Table 2 based on fluorescence spectral measurement.

TABLE 2 Exam- Excitation wavelength Emission wavelength Intensity ple(nm) (nm) (arbitrary unit) 1 344 471 1.402 2 340 478 0.930 3 335 4760.927 4 330 471 0.595 5 327 476 0.624 6 332 472 0.727 7 328 476 0.929 8328 477 0.908 9 327 472 1.057 10 324 478 1.097 11 327 477 1.048 12 330476 0.432 13 328 475 1.196 14 330 478 1.142 15 334 472 0.878 16 323 4770.803

Examples 17 to 61

Used as starting materials were the same silicon nitride powder and thesame aluminum nitride powder as Example 1, and powders of boron oxide,boron nitride, manganese carbonate, cerium oxide, praseodymium oxide,neodymium oxide, samarium oxide, europium oxide, terbium oxide, anddysprosium oxide. To obtain each composition shown in Table 3, therewere weighed predetermined amounts of starting material powders shown inTable 4, and the powders were then mutually mixed for ten minutes by amortar and a pestle both made of silicon nitride. The obtained mixturewas passed through a sieve of 500 μm, to obtain powder aggregationsexcellent in flowability. The powder aggregations were naturally droppedand loaded into a crucible made of boron nitride having dimensions of 20mm diameter and 20 mm height. Next, the crucible was set into anelectric furnace of black lead resistance heating type. There wasconducted a firing operation by firstly bringing the firing environmentto vacuum by a diffusion pump, heating from a room temperature up to800° C. at a rate of 500° C./hour, introducing nitrogen at a purity of99.999 vol % at 800° C. to achieve a pressure of 1 MPa, elevating thetemperature to 1,900° C. at a rate of 500° C./hour, and holding for 2hours at that temperature.

According to X-ray diffraction, all the obtained fired bodies included50 mass % or more of AlN or AlN solid solution, thereby obtainingphosphors emitting red light having peaks at wavelengths between 560 nmand 650 nm by excitation of ultraviolet light as shown in Table 5 basedon fluorescence spectral measurement. FIG. 7 shows an excitationspectrum and an emission spectrum of Example 27. The excitation spectrumhas a peak at 247 nm, and excitation at this wavelength leads toemission of red light at 596 nm. FIG. 8 shows a transition of anemission intensity when the phosphor was adopted and ultraviolet pumplight having a wavelength of 247 nm was blocked, after subjecting thephosphor to irradiation of the pump light for 30 seconds. The period oftime was 30 seconds during which the initial emission intensity waschanged to a 1/10 intensity, and a 1/30 emission intensity was kept evenafter 4 minutes.

TABLE 3 Designed Composition Si Al O N B Mn Ce Pr Nd Sm Eu Tb Dy Ex. a be d c a a a a a a A a 17 0 0.0005 0.0005 0.4995 0 0.0005 0 0 0 0 0 0 018 0 0.499 0.001 0.499 0 0.001 0 0 0 0 0 0 0 19 0.0286 0.4662 0.00050.5043 0 0.0005 0 0 0 0 0 0 0 20 0.0286 0.4657 0.001 0.5038 0 0.001 0 00 0 0 0 0 21 0 0.499 0.0005 0.4995 0.0005 0.0005 0 0 0 0 0 0 0 22 00.4657 0.001 0.499 0.0005 0.001 0 0 0 0 0 0 0 23 0.0286 0.4652 0.00250.5043 0.0005 0.0005 0 0 0 0 0 0 0 24 0.0286 0.4978 0.0025 0.5038 0.00050.001 0 0 0 0 0 0 0 25 0 0.4978 0.0025 0.4978 0 0.001 0.001 0 0 0 0 0 026 0 0.4978 0.0025 0.4978 0 0.001 0 0.001 0 0 0 0 0 27 0 0.4978 0.00250.4978 0 0.001 0 0 0.001 0 0 0 0 28 0 0.4978 0.0025 0.4978 0 0.001 0 0 00.001 0 0 0 29 0 0.4978 0.0025 0.4978 0 0.001 0 0 0 0 0.001 0 0 30 00.4978 0.0025 0.4978 0 0.001 0 0 0 0 0 0.001 0 31 0 0.4978 0.0025 0.49780 0.001 0 0 0 0 0 0 0.001 32 0 0.4978 0.0025 0.4978 0.001 0.001 0 0 0 00 0 0 33 0.0285 0.4646 0.0024 0.5026 0 0.001 0.001 0 0 0 0 0 0 34 0.02850.4646 0.0024 0.5026 0 0.001 0 0.001 0 0 0 0 0 35 0.0285 0.4646 0.00240.5026 0 0.001 0 0 0.001 0 0 0 0 36 0.0285 0.4646 0.0024 0.5026 0 0.0010 0 0 0 0 0 0 37 0 0.4985 0.0015 0.4985 0 0.0015 0 0 0 0 0 0 0 38 00.499 0.001 0.499 0 0.001 0 0 0 0 0 0 0 39 0 0.4966 0.004 0.4966 00.0003 0 0 0.0025 0 0 0 0 40 0 0.497 0.0035 0.497 0 0.0005 0 0 0.002 0 00 0 41 0 0.4978 0.0025 0.4978 0 0.001 0 0 0.001 0 0 0 0 42 0 0.49810.002 0.4981 0 0.0013 0 0 0.0005 0 0 0 0 43 0 0.4984 0.0018 0.4984 00.001 0 0 0.0005 0 0 0 0 44 0 0.4965 0.004 0.4965 0 0.001 0 0 0.002 0 00 0 45 0 0.494 0.007 0.494 0 0.001 0 0 0.004 0 0 0 0 46 0 0.4985 0.00180.4985 0 0.0003 0 0 0.001 0 0 0 0 47 0 0.4973 0.003 0.4973 0 0.0015 0 00.001 0 0 0 0 48 0 0.4968 0.0035 0.4968 0 0.002 0 0 0.001 0 0 0 0 49 00.4966 0.004 0.4966 0 0.0003 0 0 0 0 0 0 0.0025 50 0 0.497 0.0035 0.4970 0.0005 0 0 0 0 0 0 0.002 51 0 0.4978 0.0025 0.4978 0 0.001 0 0 0 0 0 00.001 52 0 0.4981 0.002 0.4981 0 0.0013 0 0 0 0 0 0 0.0005 53 0 0.49840.0018 0.4984 0 0.001 0 0 0 0 0 0 0.0005 54 0 0.4965 0.004 0.4965 00.001 0 0 0 0 0 0 0.002 55 0 0.494 0.007 0.494 0 0.001 0 0 0 0 0 0 0.00456 0 0.4985 0.0018 0.4985 0 0.0003 0 0 0 0 0 0 0.001 57 0 0.4973 0.0030.4973 0 0.0015 0 0 0 0 0 0 0.001 58 0 0.4968 0.0035 0.4968 0 0.002 0 00 0 0 0 0.001 59 0 0.4966 0.004 0.4966 0 0.0003 0 0 0 0 0.0025 0 0 60 00.497 0.0035 0.497 0 0.0005 0 0 0 0 0.002 0 0 61 0 0.4978 0.0025 0.49780 0.001 0 0 0 0 0.001 0 0

TABLE 4 Ex. Si₃N₄ AlN B₂O₃ BN MnCO₃ CeO₂ PrSO₁₁ Nd₂O₃ Sm₂O₃ Eu₂O₃ Tb₄O₇Dy₂O₃ 17 0 99.72 0 0 0.28 0 0 0 0 0 0 0 18 0 99.441 0 0 0.56 0 0 0 0 0 00 19 6.516 93.217 0 0 0.27 0 0 0 0 0 0 0 20 6.506 92.961 0 0 0.53 0 0 00 0 0 0 21 0 99.659 0 0.06 0.28 0 0 0 0 0 0 0 22 0 99.381 0 0.06 0.56 00 0 0 0 0 0 23 6.519 93.156 0 0.06 0.27 0 0 0 0 0 0 0 24 6.508 92.901 00.06 0.53 0 0 0 0 0 0 0 25 0.000 98.615 0 0 0.55 0.831 0 0 0 0 0 0 260.000 98.624 0 0 0.55 0 0.82 0 0 0 0 0 27 0.000 98.633 0 0 0.55 0 0 0.810 0 0 0 28 0.000 98.604 0 0 0.55 0 0 0 0.84 0 0 0 29 0.000 98.596 0 00.55 0 0 0 0 0.85 0 0 30 0.000 98.544 0 0 0.55 0 0 0 0 0 0.9 0 31 0.00098.546 0 0 0.55 0 0 0 0 0 0 0.9 32 0.000 99.274 0.17 0 0.56 0 0 0 0 0 00 33 6.461 92.218 0 0 0.53 0.793 0 0 0 0 0 0 34 6.460 92.227 0 0 0.53 00.78 0 0 0 0 0 35 6.461 92.236 0 0 0.53 0 0 0.77 0 0 0 0 36 6.459 92.2020 0 0.53 0 0 0 0 0.81 0 0 37 0 99.163 0 0 0.84 0 0 0 0 0 0 0 38 0 99.4410 0 0.56 0 0 0 0 0 0 0 39 0 97.848 0 0 0.14 0 0 2.01 0 0 0 0 40 0 98.110 0 0.28 0 0 1.62 0 0 0 0 41 0 98.633 0 0 0.55 0 0 0.81 0 0 0 0 42 098.898 0 0 0.69 0 0 0.41 0 0 0 0 43 0 99.037 0 0 0.56 0 0 0.41 0 0 0 044 0 97.836 0 0 0.55 0 0 1.61 0 0 0 0 45 0 96.277 0 0 0.54 0 0 3.18 0 00 0 46 0 99.046 0 0 0.14 0 0 0.81 0 0 0 0 47 0 98.359 0 0 0.83 0 0 0.810 0 0 0 48 0 98.086 0 0 1.11 0 0 0.81 0 0 0 0 49 0 97.635 0 0 0.14 0 0 00 0 0 2.23 50 0 97.937 0 0 0.28 0 0 0 0 0 0 1.79 51 0 98.546 0 0 0.55 00 0 0 0 0 0.9 52 0 98.854 0 0 0.69 0 0 0 0 0 0 0.45 53 0 98.992 0 0 0.560 0 0 0 0 0 0.45 54 0 97.666 0 0 0.55 0 0 0 0 0 0 1.78 55 0 95.945 0 00.54 0 0 0 0 0 0 3.51 56 0 98.959 0 0 0.14 0 0 0 0 0 0 0.9 57 0 98.272 00 0.83 0 0 0 0 0 0 0.9 58 0 97.999 0 0 1.11 0 0 0 0 0 0 0.9 59 0 97.7570 0 0.14 0 0 0 0 2.1 0 0 60 0 98.037 0 0 0.28 0 0 0 0 1.69 0 0 61 098.596 0 0 0.55 0 0 0 0 0.85 0 0

TABLE 5 Exam- Excitation wavelength Emission wavelength Intensity ple(nm) (nm) (arbitrary unit) 17 248 597 0.682 18 248 597 0.758 19 229 5960.410 20 228 597 0.444 21 242 597 0.494 22 247 597 0.783 23 230 5970.447 24 228 597 0.439 25 247 597 0.877 26 247 597 0.773 27 247 5961.014 28 248 597 0.767 29 247 596 0.806 30 247 597 0.634 31 247 5970.927 32 247 597 0.648 33 233 597 0.388 34 246 604 0.173 35 220 6020.120 36 232 598 0.421 37 239 596 0.285 38 240 597 0.261 39 239 5960.576 40 239 598 0.543 41 243 596 0.464 42 238 596 0.544 43 241 5970.459 44 239 597 0.464 45 239 596 0.604 46 247 597 0.702 47 247 5970.856 48 247 597 0.749 49 243 597 0.550 50 244 597 0.569 51 247 5970.601 52 246 597 0.589 53 244 597 0.335 54 243 597 0.356 55 243 5980.250 56 242 597 0.468 57 241 597 0.482 58 244 596 0.469 59 239 5960.167 60 239 597 0.193 61 238 596 0.255

Comparative Example will be described, in relation to above-mentionedExamples.

Comparative Example 1

Used as starting material powders were an aluminum nitride powder havinga specific surface area of 3.3 m²/g and an oxygen content of 0.79%, anda europium oxide powder having a purity of 99.9%.

The aluminum nitride powder and europium oxide powder were weighed toachieve 97.48 wt % and 2.52 wt %, respectively, to prepare a mixedpowder in the same process as Example 1, followed by loading into aboron nitride crucible. Next, the crucible was set into an electricfurnace of black lead resistance heating type. There was conducted afiring operation by firstly bringing the firing environment to vacuum bya diffusion pump, heating from a room temperature up to 800° C. at arate of 500° C./hour, introducing nitrogen at a purity of 99.999 vol %at 800° C. to achieve a pressure of 1 MPa, elevating the temperature to2,000° C. at a rate of 500° C./hour, and holding for 2 hours at 2,000°C.

The powder was measured by a spectrophotofluorometer to provide anemission spectrum and an excitation spectrum, thereby resultinglyshowing that the powder had a peak of 550 nm in the emission spectrumbased on excitation of 334 nm. The emission intensity at the peak was0.005 count. Note that the count values can be compared with oneanother, among the Examples of the present invention and the ComparativeExample. In the present invention, the count value is indicated bystandardization such that the emission intensity of a commerciallyavailable YAG:Ce phosphor (P46Y3: produced by KASEI OPTONIX, LTD.)becomes 1 upon excitation at 450 nm. This Comparative Example includesno Si in its composition, thereby exhibiting a lower emission intensityas compared with those including Si.

There will be now explained lighting instruments each adopting thephosphor comprising the nitride of the present invention. FIG. 5 is aschematic view of a structure of a white LED as a lighting instrument.The lighting instrument adopts an ultraviolet LED 2 of 380 nm as a lightemitting element, and has a structure that the ultraviolet LED 2 iscovered by a resin layer including, dispersed therein, the phosphor ofExample 1 of the present invention, and a yellow-aimed phosphor ofCa-α-sialon:Eu having a composition ofCa_(0.75)Eu_(0.25)Si_(8.625)Al_(3.375)O_(1.125)N_(14.875). Flowing anelectric current through electroconductive terminals of the LED 2 causedit to emit light at 380 nm, which excited the yellow-aimed phosphor andblue-aimed phosphor to cause them to emit yellow light and blue light,respectively, to function as a lighting instrument for emitting whitelight mixedly including the LED light, yellow light, and blue light.This lighting instrument has a higher color rendering property, since ithas a blue color component as compared with adoption of the yellow-aimedphosphor only.

There will be described a lighting apparatus prepared based on anothercomposition different from the above.

Firstly, this had a structure including: an ultraviolet LED of 380 nm asa light emitting element; and a phosphor dispersion resin layer coveredon the ultraviolet LED, the resin layer being provided by dispersing, ina layer of resin, the phosphor of Example 1 of the present invention, agreen-aimed phosphor (β-sialon:Eu) described in Example 1 of thepatent-related reference 3, and a red-aimed phosphor (CaSiAlN₃:Eu)described in Example 1 of the patent-related reference 6. Flowing anelectric current through electroconductive terminals of the LED causedit to emit light at 380 nm, which excited the blue-aimed phosphor,green-aimed phosphor, and red-aimed phosphor to cause them to emit bluelight, green light, and red light, respectively, so that the lightingapparatus functioned as one for emitting white light mixedly includingthe light from the phosphors.

There will be explained an exemplary design of an image displayingapparatus adopting the nitride phosphor of the present invention. FIG. 6is a principle schematic view of a plasma display panel as an imagedisplaying apparatus. The apparatus includes cells 11, 12, and 13 havinginner surfaces coated with a red-aimed phosphor (Y(PV)O₄:Eu), agreen-aimed phosphor (Zn₂SiO₄:Mn), and the blue-aimed phosphor ofExample 1 of the present invention, respectively. Flow of electriccurrent through electrodes 14, 15, 16, and 17 generates vacuumultraviolet light by Xe discharge within the cells, to thereby excitethe phosphor s in a manner to emit visible light of red, green, andblue, respectively, so that these light are observed from the exteriorthrough a protection layer 20, a dielectric layer 19, and a glasssubstrate 22, and thus the panel functions as an image displayingapparatus.

INDUSTRIAL APPLICABILITY

The nitride phosphors of the present invention exhibit emission of bluelight or red light different from those of the conventional sialons, andare less in luminance deterioration even upon exposure to excitationsources, thereby serving as nitride phosphors preferably usable for VFD,FED, PDP, CRT, white LED, and the like. Thus, the nitride phosphors ofthe present invention are expected to be utilized to a great extent inmaterial design of various display devices, thereby contributing todevelopment of the industry.

1. A production method of a phosphor, comprising: firing a startingmaterial mixture in a nitrogen atmosphere at a temperature range between1,500° C. inclusive and 2,200° C. inclusive, wherein the startingmaterial mixture is a mixture of metallic compounds, and is capable ofconstituting a composition comprising M, A, Al, O, and N (M is Eu; and Ais at least an element selected from the group consisting of C, Si, Ge,Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf, Ta, and W)by firing, the phosphor comprises an AlN-based crystal including anelement A including Si; Eu as a metallic element M wherein Eu isdivalent; and oxygen, the AlN-based crystal has a wurtzite-type AlNcrystal structure or a crystal structure selected from the groupconsisting of 2Hδ, 27R, 21R, 12H, 15R, and 8H, said elements A and M,and the oxygen are dissolved in the AlN-based crystal in a solid state,and the phosphor emits fluorescence having a peak at a wavelength withina range between 450 nm inclusive and 520 nm inclusive by irradiation ofan excitation source.
 2. The production method of the phosphor of claim1, wherein the mixture of metallic compounds is a mixture of: a metal,oxide, carbonate, nitride, fluoride, chloride, or oxynitride of M;silicon nitride; and aluminum nitride.
 3. The production method of thephosphor of claim 1, wherein A is Si.
 4. The production method of thephosphor of claim 1, wherein the nitrogen atmosphere is a gas atmosphereat a pressure in a range between 0.1 MPa inclusive and 100 MPainclusive.
 5. The production method of the phosphor of claim 1, furthercomprising firing the metallic compounds each in a form of powder oraggregations, after filling the metallic compounds in a container in astate where the metallic compounds are held at a filling ratioexhibiting a relative bulk density of 40% or less.
 6. The productionmethod of the phosphor of claim 5, wherein the container is made ofboron nitride.
 7. The production method of the phosphor of claim 5,wherein the aggregations have an averaged aggregation size of 500 μm orless.
 8. The production method of the phosphor of claim 1, wherein thefiring step is conducted not by means of hot-press, but exclusively bymeans of gas pressure sintering.
 9. The production method of thephosphor of claim 1, further comprising adjusting synthesized phosphorpowders in granularity, to cause the synthesized phosphor powders tohave an averaged particle size between 50 nm inclusive and 20 μminclusive, by at least one procedure selected from the group consistingof pulverization, classification, and acid treatment.
 10. The productionmethod of the phosphor of claim 1, further comprising heat treatingphosphor powder after firing, the phosphor powder after pulverizationtreatment, or the phosphor powder after granularity adjustment, at atemperature between 1,000° C. inclusive and the firing temperatureinclusive.
 11. The production method of the phosphor of claim 1, furthercomprising before the firing step, adding an inorganic compound forgenerating a liquid phase at the firing temperature or below, into themixture of metallic compounds.
 12. The production method of the phosphorof claim 11, wherein the inorganic compound for generating the liquidphase at the firing temperature or below, is at least one selected fromthe group consisting of fluoride, chloride, iodide, bromide, and atleast one kind of phosphate selected from the group consisting of Li,Na, K, Mg, Ca, Sr, Ba, and Al.
 13. The production method of the phosphorof claim 11, wherein the inorganic compound for generating the liquidphase at the firing temperature or below, is calcium fluoride oraluminum fluoride.
 14. The production method of the phosphor of claim11, wherein the inorganic compound for generating the liquid phase atthe firing temperature or below, is added at an amount between 0.1 partsby weight inclusive and 10 parts by weight inclusive, relative to 100parts by weight of the mixture of metallic compounds.
 15. The productionmethod of the phosphor of claim 1, further comprising washing a productafter firing by a solvent comprising water or an acidic water solution,to thereby decrease contents of a glass phase, second phase, or impurityphase included in the product.
 16. The production method of the phosphorof claim 15, wherein acid of the acidic water solution comprises atleast one selected from the group consisting of sulfuric acid,hydrochloric acid, nitric acid, hydrofluoric acid, and organic acids.17. The production method of the phosphor of claim 15, wherein acid ofthe acidic water solution is a mixture of hydrofluoric acid and sulfuricacid.